It is noticed that chlorine, sulfur, alkali and the like cause troubles such as preheater clogging in cement plants, and especially chlorine exerts the most harmful effect, so that a cement kiln chlorine bypass system that bleeds a kiln exhaust gas passage, which runs from the end of a cement kiln to a bottom cyclone, of a part of the combustion gas to remove chlorine is used. And, the quantity of the chlorine carried into a cement kiln increases with the increase in the amount of practical use of chlorine-content recycled resources in recent years, and increase of the capability of chlorine bypass system is inescapable.
In the chlorine bypass system, in order to extract a part of combustion gas from a portion near an entrance hood, a probe protrudes near the entrance hood and an extracted gas disposal equipment is installed in the rear stage of this probe. Since it is exposed to high temperature circumstance at approximately 1000° C. near the entrance hood, steel casting with high degree of heat resistance needs to be used for the head of this probe, or it is necessary to cool the head with cooling air taken in from the outside of the entrance hood to protect the probe.
Further, since volatile components, such as chlorine in a kiln exhaust gas is condensed to fine powder portion of bypass dust by carrying out rapid cooling to approximately 450° C. or less with the probe, a classification means such as a cyclone is arranged to a gas extraction and discharge equipment in the rear stage, and bypass dust is classified into coarse powder dust with low volatile component concentration and fine powder dust with high volatile component concentration, and the coarse powder dust is returned to a kiln system, and only fine powder dust is discharged out of the system through the chlorine bypass system to reduce the quantity of the bypass dust. Therefore, it is required to carry out rapid cooling of the kiln exhaust gas in the probe also from this point.
From the above-mentioned point of view, in the first patent document, for example, a technique is described, in which an air cooling box construction made of double tubes with many air jet holes is provided, and the entrance of the air is formed in the tangential direction of an outside tube, and the air jet holes are arranged slant so that exhaust gas flow may turn into a swirl flow.
Further, in the second patent document, a technique is described, in which in order to efficiently carry out rapid cooling of exhaust gas from a kiln bypass, a probe of double-tube structure is continued to a kiln exhaust gas passage, and a part of the kiln exhaust gas is extracted through an inner tube of this probe, and cooling gas is supplied to a fluid passage between the inner tube and an outer tube of the probe, and the cooling gas is guided to inside of a head portion of the inner tube to form a mixed rapid cooling region in a head portion of the probe.
Patent document 1: Japanese Patent Publication Heisei 11-130489 gazette (FIGS. 2 to 4)
Patent document 2: Japanese Patent Publication Heisei 11-35355 gazette (FIG. 2)